Vantaggi
My perspective is as a pretty senior developer: Good compensation - note that glassdoor only shows salary by default while at higher levels at Amazon you can get the majority of your pay from stock. If you show ownership you can take on a lot and go far quickly. Behaves like a mix of a lot of semi-coordinated startups rather than a single company. It's so giant and does so many things that you can always find something interesting to work on. It's doing really amazing work in a lot of fields and I've got a lot of confidence in the company being successful. The senior technical management is pretty impressive - a lot of the tech VP's are super technical, which is pretty valuable.
Svantaggi
There's less centralized management and fewer standard ways of doing things. This can lead to some duplication of work and lack of clarity on how to proceed. But it also results in more innovation. Culture varies a lot here - some of the old school teams are more aggressive than I like. So I've stayed out of them, which has been easy.